Transducer-transformer unit



wlannanunn WV...

ss z' 13,257,693

Nov. 22, 1966 s. M. BAGNO TRANSDUCER-TRANSFORMER UNIT 2 heets-Sheet 1 Filed July 21 19 5 INVENTOR SAMUEL M. BAGNO BY MW ATTOR EYS Nov. 22, 1966 s. M. BAGNO TRANSDUCER-TRANSFORMER UNIT 2 Sheets-Sheet 2 Filed July 21, 1965 FIG. 5

INVENTOR SAMUEL M. BA 6N0 BY M M ATTORNEYS United States Patent 3,287,693 TRANSDUCER-TRANSFORMER Samuel Meyer Bagno, 18 Columbus Ave., Bellevllle, NJ.

Filed July 21, 1965, Ser. No. 473,642

20 Claims. (Cl. 340-15) This invention relates to transducer-transformer units, and more particularly to acoustical transducers for ultrasonic space alarm systems.

Such transducers are sometimes called tweeters, but the frequency used is ultrasonic. The general object of the invention is to improve such transducers. Further objects are to provide such transducers which are compact, rugged, and inexpensive.

A more specific object is to provide such a transducer using a piezoelectric ceramic resonator, and an ancillary object is to make the transducer usable in the field to replace an older transducer of the magnetostrictive type. Another ancillary object is to provide a transformerchoke combination for efficiently coupling the input line to the ceramic resonator while making the unit appear inductive instead of capacitive, in order to correspond in impedance to the magnetostrictive transducer which is being replaced.

. More specific objects are to make the said transformer adjustable during manufacture, and to make the said choke adjustable during manufacture, these adjustments being inexpensively made independently of one another.

Another object is to provide a mounting means which affords undulatory or standing Wave vibration of a dome shaped diaphragm and which makes possible sideward displacement of the diaphragm during installation in order to facilitate external connection to a terminal strip located inside the assembly.

Still another object is to give the diaphragm a crosssection that is approximately parabolic, and to make possible two different mountings of the diaphragm. In one case the bell is used convexly and is omnidirectional, and in the other case the bell is used concavely and acts as a beamed or directional transducer.

To accomplish the foregoing objects and such other objects as may hereinafter appear, my improvement resides in the transducer-transformer elements and their relation one to another, as are hereinafter more particularly described in the following specification. The specification is accompanied by drawings in which:

FIG. 1 is a perspective view showing an omnidirectional transducer embodying features of my invention;

FIG. 2 is a vertical section taken approximately on the line 2-2 of FIG. 1;

FIG. 3 shows the bell disassembled from the base and displaced to facilitate external connection to a terminal strip in the base;

FIG. 4 is a fragmentary section drawn to large scale and taken on the line 4-4 on FIG. 3;

FIG. 5 is a section through a transformer and choke combination forming a part of the complete unit;

FIG. 6 is an electrical diagram;

FIG. 7 is an elevational view of a directional transduccr;

FIG. 8 is a section taken approximately on the line 8-8 of FIG. 7; and

FIG. 9 is explanatory of a detail of the invention.

Ultrasonic space alarm systems are already known, and require no description. A typical example of such a space system is given in German Patent No. 714,949, issued December 10, 1941, and entitled (in translation), An Arrangement for the Protection of Rooms Against Burglary and Fire by Ultrasonic Waves.

Referring to the drawing and more particularly to FIG. 1, the transducer comprises a generally bell-shaped diaphragm 12 mounted on a base 14, as by means of spaced radial studs or screws 16 received in soft rubber or equivalent grommets 18. These afford vibration of the diaphragm, but it should be understood that the diaphragm does not vibrate bodily, but rather has undulations or standing waves, the wave length being only a small fraction of the dimension of the diaphragm. In the illustrated structure the diaphragm operates at a frequency of 19 K.C., corresponding to a wave length of about of an inch, but the diaphragm has a diameter approaching five inches.

Referring now to FIG. 2, the diaphragm 12 is dome or bell-shaped, and is vibrated by a. piezo electric ceramic resonator 20, the latter being cemented to the middle of the diaphragm. A commercially available resonator may be employed, and that here shown is made of barium titanate lead zirconite. It is a thin flat disc having a diameter corresponding to one-half the wave length, or in this case about /3 inch.

Referring now to FIG. 4, the faces of the ceramic disc 20 are preliminarily coated with silver to provide electrodes 22 and 24 on opposite sides. The silver is fired in accordance with known practice. One electrical connection is shown at 26, it being soldered at 28 to electrode 24. The other electrode 22 is cemented directly to the diaphragm or bell 12, and the cement used preferably is preliminarily loaded with metallic powder in order to provide an electrical as well as a structural bond. The connection to electrode 22 then is made through the bell 12.

The input coupling to the ceramic element is made through a transformer and choke combination, and this may be described with reference to FIG. 5 of the drawing. It comprises two E-shaped cores 30 and 32 which are secured tip to tip to provide three legs 34, 36 and 38, and two closed flux paths or loops. A transformer primary 40 and a secondary 42 are located around the end leg 34 of the core, and a choke coil 44 is located around the other end leg 38 of the core. The E-shaped cores are set with cement therebetween, indicated at 46.

This structure affords adjustment of the impedance of the transformer by movement of the cores toward or away from one another at the leg 34. It provides an independent adjustment of the impedance of the choke 44 by movement or tilt of the cores toward or away from one another at the leg 38. This overall impedance adjustment is made during manufacture and preferably after connection to the ceramic resonator. The cement then sets and maintains the desired adjustment. The main reason for this adjustment is that the ceramic resonator has :a rather Wide tolerance in manufacture, and the described adjustment permits provision of a desired impedance for connection to the outside supply line, despite such variations or tolerance in the ceramic resonator.

The electric circuit is very simple, as will be seen from inspection of FIG. 6, which shows how the choke 44 is connected in series between the secondary 42 and the resonator 20. The ground iconnection indicated at 48 corresponds to the metallic bell, which most conveniently is held at ground potential.

vReverting to FIG. 2, the base 14 is cup-shaped. The spaced radial studs 16 are threaded and have screw slots at their outer ends. In the present case there are three such studs, which could be equi-distant or apart, but as shown in FIG. 3 in the present case the two lower studs are closer together. They are distributed nonuniformly to help maintain the initial orientation of the bell relative to the base, so that the wires therebetween will not be twisted when removing and replacing the bell. The cylindrical wall of the base is extruded to form collars 50 which are internally threaded to receive the screws. The screws act as studs which pass through the soft rubber grommets 18 previously referred to. The studs are threaded so that they can be turned inward free of the grommets to release the bell. It is sufficient to free two of the studs. The nuts 52 are secured to the inner ends of the screws and act as heads to limit their outward movement when restoring the bell.

The base 14 is provided with a terminal block or strip 54. The external supply comes in on conductors 56, which may be passed through protective insulating grommets 58. To facilitate connection to the terminal strip 54 the bell 12 is removed and turned aside as indicated in FIG. 3. The base may have holes for mounting screws. In preferred form a laminated sponge adhesive is employed instead of screws. The transformer choke combination, generally designated 60, is mounted on the bell 12 in the space between the bell and the base. Leads 62 extend from the combination 60 to the terminal strip 54, and these are made flexible and long enough to facilitate displacing the bell while connecting the wires 56 to the terminal strip.

Referring now to FIG. 9, the bell-shaped diaphragm 12 has a cross-section which approximates a parabola, suggested in broken lines at 64. In FIG. 2 the bell is convex and radiates omnidire-ctionally. In the form shown the bell is larger than the base and is disposed around the base. This is in contrast with the arrangement in FIG. 8 in which the bell 72 has the same configuration but is used with its concave side outermost, so that it acts as a directional or beamed transducer. In this case the base 74 again is cup-shaped, but it is deeply drawn to receive the bell 72 with space therebetween, and is larger in diameter so that the bell is received inside instead of outside the base.

The ceramic resonator 76 is cemented on the convex instead of the concave side of the bell, and the transformer-choke combination 78 also is secured on the convex side of the bell between the bell :and the base. The terminal strip 80 is secured to the bottom of the cupshaped base 74. The strip 80 may have slots instead of holes so that it can be removed when attaching the external wires thereto. The radial studs 82 again are screws threadedly received in the sidewall of the base, but in this case they have outside heads 84, because they are turned outward rather than inward to free the bell when installing the unit. As before the studs are received in grommets 86 made of soft rubber or equivalent, in order not to inhibit the desired standing wave vibration of the diaphragm. The external supply line 88 passes through a protective insulating grommet 90.

The directional transducer is used when it is necessary to avoid certain regions of turbulence, or when only a narrow specific area is to be guarded, whereas the omnidirectional transducer is used to fill a room. The directional transducer must be aimed, and for that purpose it preferably has a universal mounting, one example of which is illustrated in FIG. 7. A fixed base 92 carries a post 94 which is frictionally rotatable on the base, and this in turn carries a stud 96 pivoted :at 98 on the post 94. The stud 96 carries the cup-shaped intermediate base 74 with its concave bell 72. The base 92 may be fixedly secured on a wall, and the transducer then is aimed in desired direction, much as is done with a spot light, and indeed the universal mounting may be one of the types already developed for spot lights.

Reverting now to FIG. 3, the reason the transformerchoke combination 60 is secured to the bell 12 is so that the conductor 26 may be a short conductor which is not subject to bending. The conductors 62 may be relatively long flexible conductors. If the combination 60 were in the base 14, with long conductors carrying its output to the ceramic resonator 20, there would be a great increase in capacitance across the resonator, and the capacitance would be indefinite and changeable in amount. With the present construction the capacitance in the resonator circuit is both low and fixed.

Two of the leads 62 extend from the input wires 56 to the transformer primary. The third lead extends from the grounded mounting bracket 100 to the terminal 102 which is itself grounded at a screw 104 which helps secure the terminal strip 54 in the cup 14. It is preferred to ground the entire unit in order to prevent pick-up of stray voltages which might affect the operation of the system. The unit 60 has two output leads one of which is connected by a single short wire 26 to the resonator, and the other of which is connected to the grounded bracket 100. The connection then is through the bell 12 to that silvered face of the resonator which is adhered to the bell, as was previously described in connection with FIG. 4. Another incidental advantage of mounting combination 60 on the bell as here shown, is that the connection at 28, although soldered, nevertheless would be relatively weak against rough handling in the field, as when the bell is turned away from the base as shown in FIG. 3. With the arrangement here shown no strain is applied to the connection at 28.

In the particular example here shown the bell has a diameter of 4 inches; its cylindrical portion has a diameter of 4 inches; and its height or depth is 2% inches. It is made of aluminum having a thickness of of an inch.

The transformer core is made of ferrite, and has a length of inch, and each half has a height of inch and a thickness of inch. The end legs have a width of inch and the center leg has a double width of inch. The initial permeability is approximately 3,000. The primary has 100 turns; the secondary has 350 turns; and the choke has 600 turns, all being made of No. 36

wire.

It is believed that the construction and method of use of my improved transducer-transformer unit, as well as the advantages thereof, will be apparent from the foregoing detailed description. It will also be apparent that while I have shown and described my invention in several preferred forms, changes may be made in the structures shown without departing from the scope of the invention, as sought to be defined in the following claims.

I claim:

1. A transducer for an ultrasonic space alarm system, said transducer comprising a bell-shaped standing wave diaphragm made of sheet material, and a disc-shaped pieggelectric ceramic resonator having one flat face ce'm'ented to the middle of said diaphragm, whereby the resonator acts as a bender and the diaphragm is vibrated with standing wave undulations which propagate in the ambient air.

2. A transducer for an ultrasonic space alarm system, said transducer comprising a bell-shaped standing wave diaphragm made of sheet material, and a disc-shaped piezoelectric ceramic resonator having one flat face cemented to the middle of said diaphragm, whereby the resonator acts as a bender and the diaphragm is vibrated with standing wave undulations which propagate in the ambient air, the diameter of said ceramic resonator as adhered to the diaphragm and serving as a bender being approximately one-half the wave length of the ultrasonic frequency to be transmitted, and the said wavelength being only a small fraction of the dimension of the diaphragm.

3. A transducer as defined in claim 1, and a trans former and choke combination for coupling an outside source to the resonator, said transformer-choke combination comprising a core having three legs and providing two closed flux loops, a transformer primary and secondary on one end leg, and a choke coil on the other end leg, said choke coil being connected in series between the secondary and the resonator, the resulting transducer being inductive and adapted to replace a magnetostrictive type of transducer in the field.

4. A transducer for an ultrasonic space alarm system, said transducer comprising a diaphragm, a piezoelectric resonator to vibrate the same, and a transformer and choke combination for coupling an outside source to the resonator, said transformer-choke combination comprising two E-shaped cores secured tip to tip to provide three legs and two closed flux loops, a transformer primary and secondary on one end leg, and a choke coil on the other end leg, said choke being connected in series between the secondary and the resonator, said E-shaped cores being set with cement therebetween and affording adjustment of the transformer and of the choke prior to setting of the cement, the resulting transducer being inductive and adapted to replace a magnetostrictive type of transducer in the field.

5. A transducer as defined in claim 1, and a cup-shaped base on which the diaphragm is mounted through soft grommets on the diaphragm affording vibration, said base having spaced radial studs passing through said grommets.

6. A transducer for an ultrasonic space alarm system, said transducer comprising a bell-shaped standing Wave diaphragm made of sheet material, a disc-shaped piezoelectric resonator having one flat face cemented to the diaphragm to act as a bender to vibrate the same, a base on which the diaphragm is mounted through means affording vibration, a terminal strip in said base, a transformer and choke combination mounted on the diap a between the diaphragm and the base, leads extending from the transformer primary to the terminal strip, said leads being flexible and long enough to facilitate displacing the diaphragm while making external connections to the terminal strip.

7. A transducer as defined in claim 1, a cup-shaped base on which the diaphragm is mounted through soft grommets affording vibration, said base having spaced radial studs passing through said grommets, a terminal strip in said base, a tg agsformccand choke combination mounted on the diap ragm between the diaphragm and the base, leads extending from the transformer primary to the terminal strip, said leads being flexible and long enough to facilitate displacing the diaphragm while making external connections to the terminal strip.

8. A transducer as defined in claim 2, and a cup shaped base on which the diaphragm is mounted through soft grommets, said base having spaced radial studs passing through said grommets.

9. A transducer as defined in claim 2, a transformer and choke combination for coupling an outsideerrergy source to the resonator, said transformer-choke combination comprising two E-shaped cores secured tip to tip to provide three legs and two closed flux loops, a transformer primary and secondary on one end leg, and a choke on the other end leg, said choke being connected in series between the secondary and the resonator, said E-shaped cores affording adjustment of the tip to tip spacing and consequently the impedance of the transformer and of the choke.

10. A transducer for an ultrasonic space alarm system, said transducer comprising a bell-shaped standing wave diaphragm made of sheet material, a disc-shaped piezoelectric cegamic resonator having one flat face cemented to said diaphragm, whereby the resonator acts as a bender and the diaphragm is vibrated with standing wave undulations which propagate in the ambient air, a transformer and choke combination for coupling an outside energy source to the resonator, said transformer-choke combination comprising a core having three legs and providing two closed flux loops, a transformer primary and secondary on one end leg, and a choke on the other end leg, said choke being connected, in series between the secondary and the resonator, a cup-shaped base on which the diaphragm is mounted, a terminal strip in said base, said transformer-choke combination being mounted on the diaphragm between the diaphragm and the base, and

leads extending from the terminal strip to the transformer primary, said leads being flexible and long enough to facilitate displacing the diaphragm while making external connections to the terminal strip.

11. A transducer as defined in claim 2, a transformer and choke combination for coupling an outside"s 5 fi r eTJ the resonator, said transformer-choke combination comprising two E-shaped cores secured tip to tip to provide three legs and two closed flux loops, a transformer primary and secondary on one end leg, a choke on the other end leg, said choke being connected in series between the secondary and the resonator, said E-shaped cores affording adjustment of the tip to tip spacing and consequently the impedance of the transformer and of the choke, a cup-shaped base on which the diaphragm is mounted through soft grommets, a terminal strip in said base, said transformer-choke combination being mounted on the diphragm between the diaphragm and the base, and leads extending from the terminal strip to the trans former primary, said leads being flexible and long enough to facilitate displacing the diaphragm while making external connections to the terminal strip.

12. A transducer as defined in claim 1 in which there is a cup-shaped base on which the diaphragm is mounted through soft grommets on the diaphragm affording vibration, said base having spaced radial studs passing through said grommets, and in which the bell-shaped diaphragm has a cross-section which is approximately parabolic, and is convex and omnidirectional, the open end of said diaphragm being larger than and being disposed around the base, said base having three radial screws spaced therearound, and said diaphragm having three soft grommets receiving said screws. ,1

13. A transducer as defined in clai "6 in which the bell-shaped diaphragm has a cross-secti which is approximately parabolic, and is convex and omnidirectional, the open end of said diaphragm being larger than and being disposed around the base, said base having three radial screws spaced therearound, and said diaphragm having three soft grommets receiving said screws, said ceramic resonator and said transformer-choke combination being mounted on the concave side of the diaphragm between the diaphragm and the base.

14. A transducer as defined in claini lmin which the bell-shaped diaphragm has a cross-section which is approximately parabolic, and is convex and omnidirectional, the open end of said diaphragm being larger than and being disposed around the base, said base having three radial screws spaced therearound, and said diaphragm having three soft grommets receiving said screws, said ceramic resonator and said transformer-choke combination being mounted on the concave side of the diaphragm between the diaphragm and the base.

15. A transducer as defined in claim 1 in which the bell-shaped diaphragm is approximately parabolic in crosssection, and is disposed with its concave side outward to provide a directional or beamed transducer, and in which said diaphragm is received within a deep cupshaped base, and in which the latter is mounted by a swivel mounting on a fixed base, and in which there is a cup-shaped base on which the diaphragm is mounted through soft grommets on the diaphragm affording vibration, said base having spaced radial studs passing through said grommets.

16. A transducer as defined in claimia in which the bell-shaped diaphragm is approximately paabolic in crosssection, and is disposed with its concave side outward to provide a directional or beamed transducer, and in which it is received within a deep cup-shaped base, and in which the latter is mounted by a swivel mounting on a fixed base, and in which the ceramic resonator and the transformer-choke combination are mounted on the convex side of the diaphragm between the diaphragm and the cup-shaped base.

(17. A transducer as defined in clairnQtl lin which the bell-shaped diaphragm is approximately parabolic in crosssection, and is disposed with its concave side outward to provide a. directional or beamed transducer, and in which it is received within a deep cup-shaped base, and in which the latter is mounted by a swivel mounting on a fixed base, and in which the ceramic resonator and the transformer-choke combination are mounted on the convex side of the diaphragm between the diaphragm and the cup-shaped base.

18. A transducer for an ultrasonic space alarm system, said transducer comprising a bell-shaped standing wave diaphragm, and a cup-shaped base on which the diaphragm is mounted, the bell-shaped diaphragm having a cross-section which is approximately parabolic, and being convex and omnidirectional, the open end of said diaphragm being larger than and being disposed around the base, said base having three radial screws spaced therearound, and said diaphragm having three soft grommets receiving said screws and aifording vibration.

19. A transducer for an ultrasonic space alarm system, said transducer comprising a bell-shaped standing wave diaphragm, a piezoelectric resonator to vibrate the same, a base on which the diaphragm is mounted, a terminal strip in said base, a tra er and choke combination mounted on the diaphragm between the diaphragm and the base, leads extending from the transformer primary to the terminal strip, said leads being flexible and long enough to facilitate displacing the diaphragm while making external connections to the termnial strip, the bellshaped diaphragm having a cross-section which is approximately parabolic, and is convex and omnidirectional, the open end of said diaphragm being larger than and being disposed around the base, said base having three radial screws spaced therearound, and said diaphragm having three soft grommets receiving said screws and affording vibration of the diaphragm, said ceramic resonator and said transformer-choke combination being mounted on the concave side of the diaphragm between the diaphragm and the base.

20. A transducer for an ultrasonic space alarm system, said transducer comprising a bell-shaped standing wave diaphragm, a disc-shaped piezoelectric ceramic resonator cemented to said diaphragm, a trans cho ke combination for coupling an outside energy source to the resonator, said transformer-choke combination comprising a core having three legs and providing two closed flux loops, a transformer primary and secondary on one end leg, and a choke on the other end leg, said choke being connected in series between the secondary and the resonator, a cup-shaped base on which the diaphragm is mounted, a terminal strip in said base, said transformer-choke combination being mounted on the diaphragm between the diaphragm and the base, and leads extending from the terminal strip to the transformer primary, said leads being flexible and long enough to facilitate displacing the diaphragm while making external connections to the terminal strip, the bell-shaped diaphragm having a crosssection which is approximately parabolic, and is convex and omnidirectional, the open end of said diaphragm being larger than and being disposed around the base, said base having three radial screws spaced therearound, and said diaphragm having three soft grommets receiving said screws, said ceramic resonator and said transformerchoke combination being mounted on the concave side of the diaphragm between the diaphragm and the base.

References Cited by the Examiner UNITED STATES PATENTS 400,515 4/1889 Thomson 323-48 X 801,035 10/1905 Murdock 340-396 1,802,781 4/1931 Sawyer et al 340-10 2,498,737 2/1950 Holden 340-10 X 2,761,117 8/1956 Green 340-10 X 2,922,999 1/1960 Carlin 340-15 2,939,106 5/1960 Mason 340-10 BENJAMIN A. BORCHELT, Primary Examiner. SAMUEL FEINBERG, Examiner. P. A. SHANLEY, Assistant Examiner. 

1. A TRANSDUCER FOR AN ULTRASONIC SPACE ALARM SYSTEM, SAID TRANSDUCER COMPRISING A BELL-SHAPED STANDING WAVE DISPHRAGM MADE OF SHEET MATERIAL, AND A DISC-SHAPED PIEZOELECTRIC CERAMIC RESONATOR HAVING ONE FLAT FACE CEMENTED TO THE MIDDLE OF SAID DIAPHRAGM, WHEREBY THE RESONATOR ACTS AS A BENDER AND THE DIAPHRAGM IS VIBRATED WITH STANDING WAVE UNDULATIONS WHICH PROPAGATE IN THE AMBIENT AIR. 